v0.14.1 of the Adafruit MQTT Library for Arduino introduces subscription callbacks. This change will allow users to organize their code into separate blocks by attaching callbacks to feed and group subscriptions. Here’s a simplified example of what the change looks like:

setup() {

  // add the rest of setup code here

  // register callback for feed


loop() {

  // Ensure the connection to the MQTT server is alive (this will make the first
  // connection and automatically reconnect when disconnected).
  // See the MQTT_connect function in the full example for more info.

  // wait 10 seconds for subscription messages
  // since we have no other tasks in this example.

  // keep the connection alive


void onoffcallback(char *data, uint16_t len) {
  Serial.print("Hey we're in a onoff callback, the button value is: ");

In the example above, you can see that we added the call to mqtt.processPackets(10000);. This tells the library to wait 10 seconds (10000ms) for incoming packets before moving on to the next task, and it will block all other code execution. If your sketch is only waiting for subscription messages, then 10 seconds might be a good timeout, but if your sketch handles other tasks, you may want to reduce the timeout to 1 second (1000ms).

The full example with multiple feed subscriptions can be found in the Adafruit_MQTT Arduino Library on GitHub. You will need to install or update the Adafruit MQTT Library to version 0.14.1 in the Arduino Library Manager, and open the mqtt_esp8266_callback example to get started.

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